Characterization of altered RBP from mutant chickens will be pursued with highest priority. Amino acid analysis will be performed with particular emphasis on tryptophan and lysine--two acids involved in riboflavin binding in normal RBP. Molecular weight will be determined and peptide mapping will be attempted for comparison with pro-RBP and RBP. Heterozygote hens will be examined for both pro-RBP and altered RBP, since they have only half the normal RBP in their blood and eggs. Total deglycosylation experiments on RBP will be continued using an endoglucosaminidase. If successful, riboflavin-binding, antigenicity, and transport to the egg yolk will be studied. Also quantitative carbohydrate analysis will be performed (lower priority). An attempt will be made to define the molecular nature of the genetic mutation in rdrd chickens and to quantify the effect of Rdrd population.